An operating system consists of a set of procedures and system software modules that manage the computer system resources, ensure efficient use of these resources and offer the user a convenient interface. One can appreciate that an operating system acts as an interface between the hardware of a computer system and the user or application programs.
To act as interface between users and hardware, an operating system must be able to perform the following functions.
To enable the startup application programs. In this regard, the operating system must have: a text editor, an interpreter and a link editor.
The allocation of resources necessary to execute programs is achieved by identifying what programs are running, the need for memory, peripheral devices that are also connected to the computer and data protection requirements.
Facilities for data compression, sorting, merging, cataloging and maintenance of libraries, in other words what are the utility programs available and how the computer can use them.
Planning of the works according to certain criteria, for efficient use of CPU.
Assisting the implementation of programs through communication-user computing system, at both hardware and software level.
Operating system components
Most operating systems that have the role of hardware interface for users are organized on two levels: physical layer, which is closer to the hardware of the computer system, interfering with the system and a logic level, which is closer to the user, interfering with it by means of commands, programming languages, tools and so on.
According to these two levels, the operating systems mainly include two categories of programs:
- Command and control programs, having the role of coordination and control of all functions of the operating systems, such as input-output processes, execution breaks, hardware-user communication;
- Services programs (processing), which are performed under the supervision and control of the programmers that develop their application programs.
The first operating systems were out of processing programs. The communication operations that were to be done were in fact done through a command language that allowed the interpretation of instructions for system and error handling statements. Such systems were operating in the mono-programming. The CPU (central processing unit) can execute only one instruction in a certain quantum of time and cannot operate unless there are data inside the internal memory. The input devices are slow in providing data if the internal memory has less data written on it, thus the CPU must wait a bit until it transfers the data or the programs itself for the program execution to begin.
If the computer system has a simple operating system, then the processing is performed by several programs, leading to an inefficient use of CPU.
Types of operating systems
Basically, there are two types of personal computer operating systems: monotasking, which runs one program at a time, fulfilling two basic functions; and multitasking operating system which should provide additional performance for programs that use resource allocation and management of the resources. The main components encoutered here are: the supervisor, which launches, stops or suspends the allocations; the scheduler, which adjusts the execution time for the operations in progress; the program that allocates the resources that highlights with the help of colors the free resources or the allocated resources and the management module which is in fact the dialog program between peripherals.
